Conventional devices for the temporary handling, fixing or manipulation of items, for example by transmitting a deformation force, include, for example, tongs or shears.
Tongs are a two-membered tool, in which the active faces are configured for gripping, forming, deforming, cutting or in any other manner. Tongs generally consist of three regions, the lever arms having a respective handle, the joint and the tong head with the active faces. Generally, tongs are equipped with two-sided lever arms, which are connected to one another by a joint. As a rule, the handles in this case form the longer arms and the shorter arms form the tong head. According to the lever principle, the manual force applied to the handles is reinforced and transmitted by means of the tong head to an item.
Differing from the basic type of tongs, there are numerous special forms, some of which are also widely used, such as, for example, vice-grip locking pliers based on the knee lever principle. For example, configurations as universal pliers, pipe pliers, water pump pliers, side cutters, circlip pliers, forge tongs, flat pliers, hole punches or piston ring pliers are known.
Tongs are also widely used in the medical sector. By way of example, swab forceps can be mentioned here, which have a lock above the handle in order to fix the object grasped. In contrast to swab forceps, Magill forceps have a lateral angled portion of the gripping arms.
Furthermore, countless special tongs have been created for a wide variety of applications, such as, for example, grill tongs.
A generic device for manipulating items, also described as tongs, is known in the form of a staple remover tool, in which two pointed active faces each form a head. The front active faces of the parallel heads are, like their rear active faces, connected to one another in one piece, so the front and rear active faces can also be called a single, divided or penetrated active face.
The advantage of a plurality of heads which can be achieved in practice is primarily that by means of a plurality of engagement points determined by each head and spaced apart from one another, a possible torque about an engagement point can be better absorbed and thereby the handling, in particular of large items, can be substantially facilitated.
Devices, in particular tongs, with a plurality of heads, however, have the common drawback that the front and rear active faces of adjacent heads always move in parallel. Therefore if the object to be fixed or to be manipulated has a shaping that is not completely flat and, in addition, of a constant material thickness, the transmission of the active force is substantially limited to a single head, so the advantageous effect does not occur in the desired manner.
While the active face is rigidly connected to the lever arm in conventional tongs, DE 20 2005 006 197 U1, in comparison, describes tongs with two adjustable tong heads, it being possible to bring the tong mouths into positions which differ from one another, namely, in each case, into an opened or closed state. To thus provide tongs with a double tong head, in which two lever arms which can be adjusted to the front or rear and two tong heads are present, two tong heads can be operated by means of the handles in order to open or close a tong mouth of two respective tong jaws, the opening and closing of the tong mouth being able to be carried out simultaneously by the two respective tong jaws.
Tongs known as vice-grip locking pliers can be adjusted using an adjusting screw to an opening width and clamped in this position on the workpiece. The vice-grip locking pliers are released by an additional lever, which in turn overcomes the dead centre. U.S. Pat. No. 7,237,425 describes double tongs based on this principle of vice-grip locking pliers, the levers of which are connected in each case to a pressure plate, can be actuated independently and can be pressed against a common abutment.
These double-headed tongs are in fact an interchangeable head, because, in each case, only one head is ready to function, so only one alternative application possibility is produced.
FIGS. 1 and 2 show a plan view and a front view of conventional tongs 1 with two heads 2, 3. The heads 2, 3 are in this case arranged parallel to one another in such a way that the active faces 4, 5, 6, 7, which are configured as flat jaws here, always carry out a parallel, in other words matching, movement. In this case, a respective lever arm 8 is associated with the two upper active faces 4, 6 and a further lever arm 9 is associated with the two lower active faces 5, 7 of the parallel heads 2, 3 in relation to an object 10. The advantage of tongs 1 of this type is the two engagement points 11, 12, which allow secure handling of the object 10, in particular better transmission of occurring torques.
However, as can clearly be seen in FIG. 2, this advantage is not achieved in those objects 10 which, in the region of the two heads 2, 3, in each case have a different material thickness d, D, because a non-positive connection can then only be realised in the region of just one of the two heads 2, 3.